Method of rolling alloys



Patented Nov. 2,1937 I i UNITED STATES PATENT OFFICE METHOD or ROLLING ALLors Frederick T. McCurdy, Kokomo, Ind., assignor,

1 by mesne assignments, to Union Carbide and garllion Corporation, a corporation of New No Drawing. Application March 19, 1935,

Serial No. 11,814

2 Claims. (Cl. 80-60) The invention is a methodoi hot working alfilament type on an object in the open, no corloys of the cobalt-chromium-tungsten type. rection being made for black body radiation Cobalt-chromium-tungsten. alloys are disclosed It is usually necessary'to heat the billet to a in Patent 1,057,423 issued April 1, 1913, to Elwood temperature somewhat above the rolling tempera- 5 Haynes, and, several modifications oi the original ture to compensatefor the heat lost between the 5 alloys are known. The use of these alloys for furnace and the rolls, but this superheat should weareresistant articles has been extensive, the exbe kept to a minimum. tent being limited chiefly by difliculties in fabri- The amount of reduction which can safely be eating large articles. The alloys can be mamade in each pass through the rolls is usually not chined only with considerable difliculty and more than about 0.015 inch for each of the first l0 forged only to a very limited extent. It has herefew passes, until the billet has been reduced by tofore been believed that this material could not about 0.125 inch, and not more than about 0.03 be hot-rolled into large sheets andplates, and it inch for each subsequent pass, although somehas been necessary to shape the metal by casting, times a reduction of as much as 0.03 inch per welding, and grinding. pass may be made even in the initial passes, The 15 I- have now found that by adjusting the combillet ordinarily must be reheated to rdiling temposition, choosing the correct working temperaperature after each pass, although it is someture, and limiting the amount oi draft or rate times possible to secure a further reduction by of reduction, all within relatively narrow limits, repassing the billet once through the rolls withit is possible to hot-work cobalt-chromiumout reheating and without changing the clear- 20 tungsten alloys into relatively large sheets, plates, ance between the ,rolls. and the like. Such hot-worked products are not' In the practice of the method of the invention only betteradapted for further fabrication into I have successfully rolled billets measuring 3 certain articles than cast metal, but the properinches by 8 inches by inch, and 18 inches by y ties of the new wrought'material are unique and 18 inches by 1.25 inches down to relatively thin 25 valuable. plates and sheets. For example, the last men- 7 The preferred composition comprises approxitioned billets have been rolled down to V inch mately chromium, 5% tungsten, 1% carbon, plates having excellent surfaces and valuable and the remainder cobalt. The composition may mechanical properties.

. 30 be varied within the approximate limits of 15% The rolled material of the invention is char- 30 to chromium, 2% to 6% metal of the group acterized by high strength and great resistance consisting of tungsten and molybdenum, from to corrosion, erosion, and abrasion. Comparative very small but appreciable amounts to 1.25% tests of rolled material within the invention and carbon, the remainder chiefly cobalt with which of cast material having substantially the same there may be associated small amounts of machemical composition indicated an average ten- 3 t'erials such as iron, nickel, manganese, and s'ilisile strength of about 132,400 pounds per square con. If any one of the ingredients chromium, inch for the former material as compared with tungsten, or carbon is near the upper limit of its about 95,590 pounds per square inch for the latter respective range as given above, it is preferred material. A break test which comprised securely 40 that the other two of these ingredients be well clamping a- /2 inch square bar, leaving a 1 inch 40 below the upper limits of their specified ranges. overhang, applying a loadat the end of the over- The best rolling temperature for the preferred han an increasing the load until h r rok composition is about 2000 F. to 2050 F, .1; th indicated an average transverse strength of 4866 composition is varied within the described limits, Pounds for the rolled material as compared with the best rolling temperature will likewise va y; 02 33? for the cast mateflal' r 4 but it will be within the limits oi about 1900" F. I and about 2150" F. *n the rolling temperature is Math filming M and weal too low the billet cracks'aiong its edges; ii the sistant metal sheets and plates whichcoinpnses temperature is too high the metal is m J and hot rolling at a temperature between 1900 F. and h k uu t 2150 F. a billet of an alloy having substantially 50 tends to c ec gm the composition: 15% to 35% chromium, 2% Herein wi the appended claims the term to 6% metal of the group tungsten and molybtemperature wherever used memthe appardenum, carbon in amounts up toabout 1.25%, temperature determined by measurement and the remainder principally cobalt; the billet W l h fl pi g 0f the disappearing being reheated to rolling temperature after each 10 approximately the composition: 30% chromium.

aoemee 5% tungsten, 1% carbon, the remainder substantially cobalt; the biliet being reheated to rolling temperature after each reduction in thickness of not over about 0.015 inch until a total. reduction of about 0.125 inch has been effected,

and the billet thereafter being reheated to rolling temperature after each reduction in thickness of not over about'0'.03 inch.

..w 'r. McCURDY- 

